There are different requirements for scanning documents and films due to the ranges and the requirements of resolutions are different so that specific document scanners and specific film scanners are developed to meet the requirements.
The trend for the modem scanning devices is to include a higher resolution and a lower resolution in one scanning device. This purpose can be reached by using multiple sets of optical sensors and lenses. The purpose may also be reached by using reflection mirrors and lenses to change the paths of the light, and using masks to obstacle the paths of light and to change the paths of the light.
The devices mentioned employ multiple sets of lenses and sensors and which increase manufacturing cost. The resolution is limited by the number of sets of sensors and lenses so that the present scanners cannot meet the requirements of increase of the resolution for the needs of the market. Therefore, the conventional way by installing multiple sets of sensors and lenses in a scanning device to have a dual-resolution feature cannot catch up the requirements of market.